But the pièce de résistance, the item he most wanted to crow about, was Costco's private-label pinpoint cotton dress shirts. "Look, these are just $12.99," he said, while lifting a crisp blue button-down. "At Nordstrom or Macy's, this is a $45, $50 shirt."

IF shareholders mind Mr. Sinegal's philosophy, it is not obvious: Costco's stock price has risen more than 10 percent in the last 12 months, while Wal-Mart's has slipped 5 percent. Costco shares sell for almost 23 times expected earnings; at Wal-Mart the multiple is about 19.Mr. Dreher said Costco's share price was so high because so many people love the company. "It's a cult stock," he said.